Lota-beam cathode



March 2l, 1950 P. HAAs ET A1. 2500?988 li-BEAM cATHoDE Filed Feb. 19, 1948 Paul Haas Alberi' L. H/ZLso/l Attorney Patented Mar. 2l, 1950 UNITED STATE I-BEAM CATHODE Massachusetts Application February 19, 1948, Serial No. 9,456'

(Cl. Z50-27.5)

14 Claims.

The present invention relates to electron discharge devices and more particularly to improved forms of cathode construction of such devices.

An object of the present invention is to increase the rigidity of internal construction of electron discharge tubes having relatively long dat cathodes.

Another object of the present invention is to increase the resistance to bowing of an elongated cathode of an electron discharge device.

Still another object of the present invention is the attainment of increased cathode efficiency in an electron discharge device over that heretoiore obtainable.

In certain types of tubes, electrical requirements necessitate the use of relatively long ele'- ments, while at the same time, dimensional requirements necessitate the use of comparatively small diameter elements, closely spaced one from the other. in the prior art, it was found that while the tubes resisted shocks in the direction of their length very well, the cathode, particularly, was liable to distortion as a result of acceleration in directions transverse to the length of the tube. When the cathode was elliptical, or of elongated rectangular form in transverse cross section, the cathode was particularly vulnerable to shock or acceleration in a direction normal to the major transverse dimension of the cathode.

In accordance with an aspect of the present invention, we provide a cathode, for use in such tubes, which is in cross section in the form of a hollow I. The cathode may thus be said to be an Lbeam cathode.

Such a cathode may be constituted by attaching to the short transverse dimension of a hollow rectangular tube, metallic re-enforcing strips wider than the short dimension of the tube, and preferably of thicker material than the rectangular tube. These strips are welded or otherwise attached to the cathode tube so that their edges extend past the sides of the tube. In an end view the tube has the conformation of a i Using cathode structures as known more grid like electrodes and installed within an evacuated casing.

The present invention will be more fully understood by reference to the following detailed description which is accompanied by a drawing in which:

Fig. 1 illustrates, partially in section, an elevational View oi an electron tube embodying the present invention, while Fig. 2 is a transverse section of the tube shown in Fig. l, taken along the lines 2-2 of Fig. l, and

Fig. 3 is a fragmentary elevation of a modification of the structure of Fig. 1.

In Fig. l there is shown an electron discharge tube generally identined by reference character iii. The tube includes, within anl evacuated casing l i, an indirectly heated cathode i2 sur# rounded by a number of ancillary electrodes such as a control grid M and a plate or anode I6. If desired, additional grids may be provided between the control grid lll and the anode l5. The cathode, control grid, and anode are maintained within the envelope ll in their proper relative position by means of insulating spacers E8 and I9 through which pass support-rods for the grid and plate, while cathode l2 itself extends through the insulating spacers I8 and I9. The cathode is heated by an insulated heater wire 22 within its hollow interior, and adapted to be connected to a suitable source of electrical energy by leads 23 extending through the base of the tube envelope. Additional leads, such as leads 24, are provided for connection to the anode, cathode, and control grid.

The cathode l2 may be constructed of a length of thin-Walled rectangular tubing 26 having secured to the short sides thereof metallic reeniorcing strips 3i) and 3l. Preferably metallic strips 3G and 3! are considerably thicker than the thickness of the rectangular tubing 26 forming the body of the cathode and somewhat wider than the shorter transverse dimension of tubing 2G. Thus, as shown more clearly in Fig. 2, the tubing 26 and metallic strips 3l! and'! form an I-beam structure which has improved resistance to bowing along its length. The usual emitting coating carried by the tubular cathode is confined to the long faces of the rectangular tubing 2li between the metallic strips 3l) and 3l. Its depth is preferably equal to the distance that the metallic strips extend past the sides of the tubing. Thus, the exterior of the completed cathode is substantially rectangular in conguration. If desired, in manufacturing the cathode, the thickness of the emitting coating maybe 3 definitely determined by striking a straight edge along the edges of strips 30 and 3 l.

As indicated in Fig. 1, the strips 30 and 3| are preferably slightly shorter in length than the distance between spacers i8 and I9. Thus, short spaces, such as that indicated by reference nu meral 33, are left at the top, and/ or'bottom, of strips 3D and 3l. Some such spacing is desirable, as otherwise when the cathode is heated and exe pands longitudinally, the spacers I8 and i9 will either be forced further apart or the cathode may be placed under suicient columnar stress to cause it to bow.

In the modication of the invention shown in Fig. 3, the same reference characters are applied to parts which correspond to those already described with reference to Fig. 1. Thus, it will not be necessary to again describe these parts in detail. However, in Fig. 3 the metallic strips '30 and ,3| are extended through the cathode aperture in spacer i8 in the form of lugs 40 and lll which` may, if desired, bevbent outwardly from the cathode sleeve 26 to a slight extent, to serve a`s1 a"rneans for anchoring the cathode sleeve in position.

While we `have shown and particularly described a number of embodiments of our invention, it is to be distinctly understood that our inverition is not limited thereto, but that modicationswithin the scope of the invention may be made.

' What we claim as our invention is: A, ,y y 1, Anindirectly heated cathode including-1an elongated hollowrectangularmetal tube, a strip di'rfjnietal's'ecured. on eachof a pair of opposing sides of said tubesaid strips being wider than said sides-if .Y f

Anindirectly heated cathode including an elongatedhollow rectangular metal tube, a strip of metal secured on .each of a pair of opposing 'sidesof ,said,tube, said strips being of thicker material than said tube and wider than said sides.

indirectly heated cathode including an elongated hollow rectangular conductive tube, a strip of metal secured on each of a pair ofopposingsides of said tube, said strips beingof thicker ,materialthan said tube and wider than said sides, and electron emissivematerial on thel other sides ofsaid tube. 4.I Any indirectly ,elongated hollow rectangular tube, a strip Vof material secured on each of a` pair of opposing sides of said tube, said stripsk being of* thicker material than said tube and wider -than said slides .of said tube, the surface of said Vmaterial 'being flush with the edges of said strips. Y

An indirectly heated cathode including an elongated hollow rectangular metal tube, a strip r( )Lrnetal secured on each of a pair of opposing vsidesof said tube, said strips being of thicker material. than said tube `and wider than said si'lesand electron emissive` materialen the other /sidesotA said tube, the. surface of said material being flush with the edges of said strips, said 'istripsbeing shorter than the length ci saidtube. 6. An electron discharge device including an yelongated cathode,-an anode coaxially arranged about said cathode, said cathode being in the form pian elongated hollow rectangular metal tube, aidcathode .passing through insulating spacers ateach endthereof, said cathode having apstrip ofmetal secured on each of a pair of opposing sides' of said tube, said strips being of thicker material than said tube and wider than said sides.

heated'cathode including an Y sides, ,andelectron emissive material on ther other 7. An electron discharge device including an elongated cathode, an anode coaxially arranged about said cathode, said cathode being in the form of an elongated hollow rectangular metal tube, said cathode passing through insulating spacers at each end, said cathode having a strip of metal secured on each of a pair of opposing sides of said tube, said strips being of thicker material than said tube and wider than said sides, and electron emissive material on the other sides of said tube.

8. An electron discharge device including an elongated cathode, an anode surrounding said cathode, said cathode being in the form of an elongated hollow rectangular metal tube, said cathode passing through insulating spacers at each end, said cathode having a strip of metal secured on each of a pair of opposing sides of said tube, said strips being wider than said sides, and electron emissive material on the remaining sides of said tube, the surface of said material being flush with the edges of said strips.

9,'An electron discharge device including an elongated cathode, an anode surrounding said cathode, said cathode being in the form of an elongated hollow rectangular metal tube, said cathodepassing through insulating spacers at each end, said cathode having a strip of metal secured on each of a pair of opposing sides of said tube, and electron emissive material on the remaining sides of said tube, the surface of said material being ilush with the edges of said strips, said strips ybeing slightly shorter than the distance between said insulating spacers. HlllmAn electrn discharge device including an elongated cathode, an anode surrounding' said cathode, said 'cathode being in the form 'of an elongated hollow rectangular metal tube, vsaid cathode passing through insulating spacers Yat each end, said cathode having a strip of metal secured on each of a pair of opposing sides of said tube, said strips being wider than said sides, and Aelectron emissive material on the remaining sides Vof said tube, said strips being bent away from said tube after passing through said spacers.

ll. An electron discharge device including a cathode and a number of ancillary electrodes, said cathode beingn'the form of an elongated hollow tube having an I cross section, there being electron emissive material along the Side portions of the I, the surface of said material being flush with the edges of the tube.

12. An electron discharge device including a cathode and a number of ancillary electrodes surrounding said cathode, said cathode being in the form of an elongated hollow metal tube having a cross section in the form of a hollow elongated rectangle, and a metal strip along each of a pair of opposite sides of the tube, said strips being of thicker material than the material of said tube and wider than said sides.

13. An electron discharge device including a cathode and a number of ancillaiy electrodes surrounding said cathode, said cathode being in the form of an elongated hollow metal tube having a cross section in the form of a hollow elongated rectangle, and a conductive strip along at least one of the narrow sides of the tube, said strip being of thicker material than the material oifsaid tube and wider than the narrow sides, electron emissive material on the wide sides of said tube, and means within said tube for heating said cathode. 14. An electron discharge device including a cathode and a number of ancillary electrode sur- The following references are of record in the REFERENCES CITED le of this patent:

UNITED STATES PATENTS Number Name Date Ross Nov. 10, 1936 Haller Dec. 6, 1938 

